In the field of dentistry, one of the most important and delicate procedures is that of cleaning or extirpating a diseased root canal to provide a cavity which is substantially free of diseased tissue and antiseptically prepared for a permanent embalming or obturation to seal off the area. When done properly, this step enables subsequent substantially complete filling of the canal with biologically inert or restorative material (i.e., obturation) without entrapping noxious tissue in the canal that could lead to failure of the therapy.
In a typical root canal procedure, the sequence is extirpation of diseased tissue and debris from and adjacent the canal followed by obturation. Often there is an intermediate filling of the canal with a calcium hydroxide paste for sterilization and reduction of inflammation prior to obturation and final crowning. In performing the extirpation procedure, the dentist must gain access to the entire canal, shaping it as appropriate. However, root canals often are very small in diameter, and they are sometimes quite curved with irregular dimensions and configurations. It is therefore often very difficult to gain access to the full length of the canal and to properly work all surfaces of the canal wall.
Many tools have been designed to perform the difficult task of cleaning and shaping root canals. Historically, dentists have used elongate, tapered endodontic files with helical cutting edges to remove the soft and hard material from within and adjacent the root canal area. Such root canal dental procedures often result in overly aggressive drilling and filing away of otherwise healthy dentin wall or physical structure of the tooth root, thereby unduly weakening the integrity or strength of the tooth. Additionally, when performing root canal procedures, it is desirable to efficiently debride or render harmless all dead, damaged, or infected tissue and to kill all bacteria, viruses and/or other undesirable biological material within the root canal system. Illustrations of a typical root canal system are shown in FIGS. 1A and 1B. The root canal system includes the main root canal 1 and many lateral or accessory canals 3 that branch off of the main canal 1, all of which can contain diseased or dead tissue, bacteria, etc. It is common during root canal procedure to mechanically strip out the main canal nerve, often tearing it away from the lateral canal nerves, much of which can then stay in place in the canal and become the source of later trouble. Thereafter, the main canal 1 is cleaned and extirpated with a tapered file. While it is desirable to extirpate all of the main and accessory canals in a root canal system, some of the lateral canals 3 are very small and extremely difficult to reach in order to remove tissue. Such lateral canals are often perpendicular to the main canal and may bend, twist, and change cross-section as they branch off from the main canal, making them practically inaccessible to extirpation with any known file or other mechanical device. Accordingly, lateral canals are often not properly extirpated or cleaned. Many times no effort is made in this regard, relying instead on chemical destruction and embalming processes to seal off material remaining in these areas. This approach is sometimes a source of catastrophic failure that can lead to loss of the tooth and other problems. Further, when the main canal is extirpated with a tapered file, this action can leave an undesirable smear layer along the main canal which can plug some of the lateral canal openings and cause other problems that trap noxious material against later efforts to chemically disinfect the canal.
Dentists can attempt to chemo-mechanically debride and/or sterilize both main and lateral canals using a sodium hypochlorite solution or various other medicaments that are left in the root canal system for 30 to 45 minutes a time following primary mechanical extirpation of nerve and pulp tissue. However, this approach does not necessarily completely debride or render harmless all of the lateral root canals and material trapped therein because of the difficulty in cleaning off the smear layer and/or negotiating and fully wetting the solution into some of the smaller twisted lateral canals. As a result, many treatments using this method fail over time due to reoccurring pathology. This often requires retreatment and sometimes loss of the tooth.
Attempts have been made to reduce or eliminate the use of endodontic files and associated drawbacks by using lasers in the performance of root canal therapy. Some of these approaches involve burning away or carbonizing diseased and other tissue, bacteria, and the like within the canal. In these approaches, laser light is said to be directed or focused into or onto the diseased tissue, producing very high temperatures that intensely burn, carbonize, ablate, and destroy the tissue. These ablative treatments using high thermal energy to remove tissue often result in damage to the underlying collagen fibers and dentin of the root 5, even fusing the hydroxyapatite which makes up the dentin. In some cases, such treatments can cause substantial heating of the periodontal material and bone 7 surrounding the tooth, potentially causing necrosis of the bone and surrounding tissue. Additionally, the high temperatures in such treatments can melt the walls of the main canal, often sealing off lateral canals, thereby preventing subsequent treatment of lateral canals. Other attempts to use lasers for root canal therapy have focused laser light to a focal point within fluid disposed within a root canal to boil the fluid. The vaporizing fluid creates bubbles which erode material from the root canal when they implode. Such treatments which must raise the fluid temperature above the latent heat of vaporization significantly elevate the temperature of the fluid which can also melt portions of the main canal and cause thermal damage to the underlying dentin, collagen, and periodontal tissue. The damage caused to the tooth structure by these high energy ablative laser treatments weakens the integrity or strength of the tooth, similar to endodontic treatment utilizing endodontic files.
Therefore, there is a present and continuing need for minimally invasive, biomemetic, dental and medical therapies which remove diseased tissue and bacteria from the main root canal as well as the lateral canals of the root canal system while leaving the biological structures undamaged and substantially intact.